Process for protecting wool from yellowing by applying dibutyl butane-phosphonate



United States Patent Mayo K. Walden, El Cerrito, and Harold P. Lundgren,Berkeley, Calif., assignors to the United States of America asrepresented by the Secretary of Agriculture No Drawing. Application June23, 1954, Serial No. 438,888

1 Claim. (Cl; 117-141) (Granted under Title 35, U. S. Code (1952), sec.266) A non-exclusive, irrevocable, royalty-free license in the inventionherein described, for all governmental purposes, throughout the world,with the power to-grant sublicenses for such purposes, is hereby grantedto the Government of the United States of America.

This invention relates to a process for protecting wool from yellowingwith age.

It is well known in the art that when wool is originally prepared byscouring and other necessary cleaning methods from raw fleece, it isessentially white in color. However, upon aging the wool does not retainits whiteness but gradually becomes more and more yellow. This colorchange is of course undesirable and restricts the use of wool mainly toapplications wherein it is used in a dyed condition. It is believed thatthe yellowing of wool and other protein fibers is caused at least inpart by the action of light on the fibersthe light in some way causingor accelerating chemical changes which give rise to colored compounds.

It has now been found that if wool is treated with an ester of aphosphorus-containing acid, the tendency of the fiber to turn yellow isgreatly diminished or even eliminated completely. As disclosedhereinafterin more detail, the fiber may be subjected to acetylatingreagents prior to the treatment with the ester, thus toenhance theprotective effect. Another alternative is to remove the major part ofthe ester after subjecting the ester-treated fiber to a treatment tocause chemical combination of a minor part of the ester with the fiber.

The esters used may be derived from various phosphorus-containing acids,for example, orthophosphoric acid, pyrophosphoric. acid, triphosphoricacid, tetraphosphoric acid and organic phosphonic and phosphinic acidssuch as .benzene phosphonic acid, butane phosphonic acid, ethanephosphonic acid, dibenzene phosphinic acid, di-butane phosphinic acid,di-ethane phosphinic acid, and so forth. The alcohol (or phenol) moietyof the compounds may include radicals of the aliphatic, aromatic,alkaryl, aralkyl, or cycloaliphatic types as for example ethyl, propyl,butyl, amyl, hexyl, phenyl, benzyl, methylphenyl, cyclohexyl, and soforth. Included are esters wherein different radicals are attached tothe acid moiety and also included are esters wherein thephosphorus-containing acid is only partly esterified. Some particularesters are, for example, triethyl phosphate, tripropyl phosphate,tributyl phosphate, triamyl phosphate, trihexyl phosphate, tricyclohexylphosphate, triphenyl phosphate, tribenzyl phosphate, tritolyl phosphate,butyl diethyl phosphate, amyl diethyl phosphate, hexyl diethylphosphate, butyl diphenyl phosphate, amyl diphenyl phosphate, hexyldiphenyl phosphate, dibutyl ethyl phosphate, diamyl ethyl phosphate,dihexyl ethyl phosphate, dibutyl phenyl phosphate, diamyl phenylphosphate, dihexyl phenyl phosphate, dibutyl hydrogen phosphate, diamylhydrogen phosphate, dihexyl hydrogen phosphate, tetraethylpyrophosphate, tetrapropyl pyrophosphate, tetrabutyl pyrophosphate,tetraamyl pyrophosphate, tetrahexyl pyrophosphate, tetracyclohexylpyrophosphate, tetraphenyl pyrophosphate, tetrabenzyl pyrophosphate,tetratolyl pyrophosphate, butyl triethyl pyrophosphate, amyl triethylpyrophosphate, hexyl triethyl pyrophosphate, butyl triphenylpyrophosphate, amyl triphenyl pyrophosphate, hexyl triphenylpyrophosphate, dibutyl diethyl pyrophosphate, diamyl diethylpyrophosphate, dihexyl diethyl pyrosphosphate, dibutyl diphenylpyrophosphate, diamyl diphenyl pyrophosphate, dihexyl diphenylpyrophosphate, tributyl ethyl pyrophosphate, triamyl ethylpyrophosphate, trihexyl ethyl pyrophosphate, tributyl phenylpyrophosphate, triamyl phenyl pyrophosphate, trihexyl phenylpyrophosphate, diethyl benzenephosphonate, dipropyl benzenephosphonate,dibutyl benzenephosphonate, diamyl benzenephosphonate, dihexylbenzenephosphonate, dicyclohexyl benzenephosphonate, diphenylbenzenephosphonate, dibenzyl benzenephosphonate, ditolyl benzenephonate,diethyl butanephosphonate, dipropyl butanephosphonate, dibutylbutanephosphonate, diamyl butanephosphonate, dihexyl butanephosphonate,dicyclohexyl butanephosphonate, diphenyl butanephosphonate, dibenzylbutanephosphonate, ditolyl butanephosphonate, and so forth.

It is to be noted that not all of the esters of phosphoruscontainingacids have equal etficacy for reducing the yellowing tendency of proteinfibers. It has been observed, for example, that those esters containingbutyl groups exhibit greater effectiveness than those compoundscontaining ethyl or cresyl radicals. Compounds which are pre ferred asexhibiting greatest effectiveness are tributyl phosphate anddibutylbutanephosphonate, the latter being preferred.

In applying the ester to the fiber, any conventional technique can beused to effectuate a coating or impregnation of the fiber with theester., The ester may be applied as such or in the form of a solution ordispersion thereof. Thus dipping, spraying, or brushing techniques canbe used. The ester may be dissolved in an organic solvent such asethanol, carbon tetrachloride, chloroform, etc. and this solutionapplied to the fiber. Generally, more effective results are obtained ifthe dibutyl butanephosphonate is dissolved in water and this aqueoussolution applied to the fiber. Normally a solution containing about 1 to5% of the ester is used, the wool is soaked therein for about one day,removed, and pressed dry.

One embodiment of this invention involves a procedure wherein theester-impregnated fiber is subjected to a fixation treatment and thenthe excess of the ester is removed. This technique is advantageous as itimproves the quality of the fiber. Thus when the fiber is impregnatedwith some esters the fiber tends to develop a somewhat greasy or oilyfeel which would make the fiber less desirable for some applications. Bysubjecting the impregnated fiber to the fixative treatment and thenremoving excess ester, the greasy oroily feel is completely removed andthe resulting fiber can be used in any textile application. The fixativetreatment involves subjecting the impregnated fiber to light, preferablyin the ultraviolet region. This irradiation causes a chemical reactionbetween the fiber molecules and the ester whereby some of the esterbecomes chemically bound to the fiber. This chemical modification of thefiber causes it to resist yellowing by the action of light. After theirradiation is completed, the excess of ester on the fiber is removed bywashing with an organic solvent such as ethanol, acetone, chloroform,carbon tetrachloride, ethylene dichloride, etc. The iemoval of theunreacted ester does not decrease the yellowing resistance of the fiberbecause the chemically bound ester remains in the fiber.

It has also been found that improved resistance to yellowing is obtainedif the fiber is subjected to acetylation prior to impregnating it withthe ester. The reason for the desirable etfect of acetylation is notknown but experimental data indicate that acetylation has a synergisticeffect on the prevention of yellowing by treatment with the ester.Acetylation of the fiber can be performed by methods well known in theart, for example by subjecting the noer to reaction at to 100 C. with anacetylating agent such as acetic anhydride or ketene. Usually the woolin its normal, undried condition, containing about 812% H2O, issubjected to the acetylating reagent. The latter for better contact, maybe dissolved in an inert solvent such as formamide, glacial acetic acid,carbon tetrachloride, etc.

It is evident that the process of this invention can be applied to theprotein fiber in any physical form. Thus the process may be applied tofibers as such or to thread, yarn, Woven or knitted fabrics, felts, andso forth.

The following examples demonstrate the invention in greater detail.

Example I A sample of wool was formed into pads having a weight of 1.5g. One of the wool pads was placed in 50 cc. of acetic anhydride andallowed to stand therein at 90 for 1 hour to acetylate the wool. Theacetylated wool was then washed with water and pressed dry. Theacetylated wool was then soaked 1 day in a 1% aqueous solution ofdibutyl butanephosphonate then removed from the solution and presseddry. This product was labeled I-A.

Another wool pad was given the treatment with the dibutylbutanephosphonate solution as above without the prior acetylation. Thisproduct was labeled I-B.

The treated samples and a sample of the untreated wool (control),labeled I-C, were then subjected to a mercury vapor lamp as a source ofultraviolet rays thus to measure their resistance to yellowing. Afterexposure to the ultraviolet light, the samples were then subjected toreflectance measurements with a photometer to measure the percentage oflight reflected from the samples. The reflectance values are an index ofthe whiteness of the wool; the higher the proportion of light reflected,the whiter the wool. The results obtained are tabulated Pieces of woolflannel cloth were acetylated by soaking V 4 in acetic anhydride for 1hr. at C. The acetylated cloth was then washed and pressed dry (sampleA).

One piece of the acetylated cloth was soaked 13 hrs. in a 1% aqueoussuspension of tributyl phosphate then pressed dry (sample B).

One piece of the original flannel cloth (not acetylated). was soaked 13hrs. in a 1% aqueous suspension of tributyl phosphate then pressed dry(sample C).

The above samples plus a piece of the original cloth as a control(sample D) were then subjected to ultraviolet irradiation.- Theirradiated samples were then subjected to reflectance measurements todetermine their relative Example III A sample of wool was soaked in a 1%aqueous suspension of tributyl phosphate for 1 day. The wool was thenpressed dry and subjected to ultraviolet irradiation for 6 days. Theirradiated sample of wool was then washed with ethanol to removeunreacted tributyl phosphate. The wool was then exposed to ultravioletirradiation for 48 hours. Reflectance measurements were then made onthis sample and on a sample of untreated wool which had been irradiatedfor the same time. It was found that the treated sample had areflectance of 26% whereas the untreated control had a reflectance ofless than 20%. 7

Having thus described the invention, what is claimed is: I A process forprotecting wool from yellowing which comprises soaking wool in anaqueous solution containing about 1 to 5% of dibutyl butanephosphonatefor about one day to impregnate the wool with sufficient dibutylbutanephosphonate to make the wool resistant to yellowing, removing theWool from the solution and pressing it dry.

References Cited in the file of this patent

